Re: gdb: hardware watchpoints not working

[Vitaly Shevtsov <shev.vt1984%gmail.com@localhost>]

Is there any way to make it work under an unprivileged user? Maybe
some sysctl settings?

On Fri, Aug 30, 2024 at 12:50 AM Christos Zoulas <christos%astron.com@localhost> wrote:
>
> In article <ZtBu-aGn8H_ZWHfr%exadelic.gatalith.at@localhost>,
> Thomas Klausner  <wiz%NetBSD.org@localhost> wrote:
> >Hi!
> >
> >I just tried in gdb to watch a memory location.
> >
> >(gdb) watch *0x78f2d98cd040
> >Hardware watchpoint 6: *0x78f2d98cd040
> >(gdb) c
> >Continuing.
> >Couldn't write debug registers: Operation not permitted.
> >Command aborted.
> >(gdb)
> >
> >Watching an expression worked
> >(gdb) watch tws->dirs[0]->name
> >Watchpoint 5: tws->dirs[0]->name
> >...
> >but doesn't work for my use case because
> >
> >Watchpoint 5 deleted because the program has left the block in
> >which its expression is valid.
> >
> >and I think the variable is changed outside somehow.
> >
> >That's on gdb 15.1, NetBSD 10.99.12/amd64/20240827.
> >
> >Is this expected to work?
> >Is this a PAX issue and I need to disable (some of) it?
>
> Works as root...
>
> (gdb) watch x
> Hardware watchpoint 2: x
> (gdb) c
> Continuing.
>
> Hardware watchpoint 2: x
>
> Old value = 0
> New value = 1
> main () at sleep.c:11
> 11                      sleep(1);
> (gdb) c
> Continuing.
>
> Breakpoint 1, main () at sleep.c:10
> 10                      x++;
> (gdb) c
> Continuing.
>
> Hardware watchpoint 2: x
>
> Old value = 1
> New value = 2
> main () at sleep.c:11
> 11                      sleep(1);
> (gdb) q
> A debugging session is active.
>
>
> christos
>